This application relates generally to a system and method for handing off a mobile node and more particularly to a handoff framework to support real-time delay critical services in a next generation wireless network.
In data networks, such as Internet Protocol (IP) networks, mobile users are typically assigned to a particular class of service (such as Platinum, Gold, or Silver) based on a service level agreement (SLA) with their service provider. In a fixed network, it is relatively easy to engineer and assign the user an appropriate amount of network resources so that the SLA can be maintained at all times. However, mobility and the air-interface being utilized make the problem more difficult because the network resources have to be reassigned and/or renegotiated as the user moves from one cell to another. Additionally, the inherent hostile nature of the air-interface makes it difficult to predict and react accordingly to the changes in the radio frequency (RF).
Historically, there have been two methods to support mobility across wireless cells. In the first method, a mobile node is in the full control of the decision making and the target selection process while moving from one cell to the other. In Global Systems for Mobile Communications (GSM) or North American Time Division Multiple Access (NA TDMA) terminology this method is known as reselection. In a reselection process, the mobile node and the network have a master-slave relationship where the mobile node decides which cell serves its interest best. The network does not really have control over the target cell selection and so it is alerted to the mobile node""s decision only after the target cell is selected. As a result, reselection is typically more time consuming from a network resource allocation point of view. Also, reselection during an active session requires the network to temporarily buffer the data destined for the mobile node. Additionally, the target cell may not even have enough resources to address the resource needs of the mobile node.
In the second method, the network, along with input from the mobile node, decides when and where to handoff the mobile node. Handoff refers to the transfer of an ongoing wireless call from one transmission site (cell) to another without disconnecting the call. This method requires constant monitoring of the mobile node""s signal strength as well as complex management of target selection and network resource assignment. Network directed handoff also requires more messaging over the air compared to reselection. However, this kind of mobility support can work faster because the target is known before the actual handoff takes place. Also, the resource allocation and appropriate reservation can be done at the target to meet the mobile node""s demand. In a variation of this scheme in GSM and NA TDMA, the mobile node assists the network by periodically sending it RF related information regarding the mobile nodes"" neighboring cells. This facilitates the decision making process at the network and is called Mobile Assisted Handoff (MAHO).
The reselection based mobility works fine when the mobile node is idle or in a non-real time active session. However, as previously mentioned, reselection may result in considerable delays. Thus, buffering data for a synchronous real time application (such as voice or video) during this delay interval is not recommended. As such, over the period of a few seconds of reselection related delay, several voice packets may be dropped resulting in audible speech clipping. The reselection mechanism does not have any control over the availability of the network resources at the target cell. Additionally, in the current General Packet Radio Service (GPRS) network model, the reselection process does not prioritize resources based on the user""s SLA. To address Quality of Service (QoS) requirements for real-time, delay-sensitive multimedia services, the handoff mechanism needs to be optimized and enhanced in next generation wireless data (IP) networks.
Therefore, an improved system and method to support the handoff of a mobile node utilizing real-time delay-critical services in a next generation wireless data network is desired to reduce or eliminate the aforementioned complexities and limitations.
In response to these and other complexities and limitations, provided herein is a unique system and method for handoff of a mobile node utilizing real-time delay-critical services in a next generation wireless data network.
In one embodiment, the system includes a core network (CN) coupled to a radio access networks (RAN) which serves a mobile node. The RAN examines overload factors in the system and the CN examines admission capabilities to neighboring RANs. A traffic situation of cells (or nodes) in the neighboring RANs is determined and a new user is admitted to one of the neighboring cells based on results of the examinations and the determination. The overload factors include a radio frequency resource availability value, the user""s service profile, an existing application""s traffic characteristics, and the user""s priority. An admission control function is also provided to interact with entities in the RAN and in the CN.
In some embodiments, the system comprises a first Radio Network Controller (RNC) in the first RAN, where the first RNC provides a quality of service to a second RNC in a second RAN that is coupled to the first RNC and to the CN. Policy information is exchanged via an interface between the CN and the RNCs.
In other embodiments, the system comprises a means for prioritizing the handoff based on a user""s service level agreement and on an application being utilized by the user; a means for performing the handoff, where the handoff of a data call receives priority for resources in an entering cell in the wireless network; and means for maintaining the user""s service level agreement in the entering cell. A means for utilizing admission control to improve the management of the, for example, radio frequency resources is utilized. The admission control includes admitting a new user, admitting a new radio access channel, and admitting a new radio link.
In further embodiments, the system comprises a means for synchronizing, by the CN, data packets to be transmitted; a means for concurrently transmitting the data packets to a source RAN and a destination RAN that are coupled to each other and to the CN; a means for halting the transmission of the data packets to the source RAN if the handoff to the destination RAN is successful; and a means for receiving, by the mobile node, the data packets via the destination RAN.
In additional embodiments, the system comprises a means for allocating reserved resources in a cell in the network and a means for providing the reserved resources to a user of non-critical data traffic when the user enters the cell, where the resources are provided based on the user""s service level agreement.